Lymph Node Pathology Flashcards
(52 cards)
List 3 examples of secondary lymphoid tissue
Lymph nodes
Spleen
MALT
What are some common sites of MALT?
Tonsils, adenoids
Along GIT
Airways
Describe the histological appearance of a naive B cell vs. an activated B cell
Naive: small, blue, not much cytoplasm
Activated: larger, different morphology
What is a primary follicle in the context of a lymph node?
A dense cellular aggregation composed of inactive small resting B cells (their condensed nuclear chromatin gives the follicle a blue colour)
What is a secondary follicle in the context of a lymph node?
Secondary follicles consist of a pale centre called the germinal centre, surrounded by a darker zone known as the mantle zone
What is the structure of the mantle zone?
The mantle zone is made up of small resting B cells, the condensed nuclear chromatin producing the dark blue colour
What is the role and structure of the germinal centre?
The germinal centre is the site of B cell activation, clonal expansion and differentiation and consists of dividing B cells which are larger and paler than the small inactive lymphocytes of the marginal zone
Describe the structures found in a lymph node
External fibrous capsule: oval, well-circumscribed
Afferent and efferent veins and arteries, as well as the efferent lymphatic vessel: enter and leave at the hilum
Afferent lymphatics: enter around the outside of the node through the capsule, bring in APCs and Ag (which then travel through to the B and T cell areas)
Veins and arteries: form sinuses (cortical and inner medullary) which percolate through the node
B and T cell areas (cortex and paracortex respectively)
Inner medulla: with medullary sinuses and extensions of the B and (mostly) T cell areas called the medullary cords
Medullary cords: final differentiation into plasma cells occurs here (immunoblasts can be seen)
What happens in a germinal centre and after?
Following appropriate stimulation by APCs or Ag, naive B lymphocytes from the mantle zone undergo clonal expansion and differentiation into centroblasts, centrocytes then immunoblasts. Somatic hypermutation and heavy chain class switching occur From the GC, the activated B cells migrate to the medullary cords where they complete their differentiation into plasma cells (or some cells become memory B cells)
What are the paler areas within the GC?
Macrophages containing phagocytosed apoptotic cells (called tingible body macrophages)
What other cells (besides B cells) are located within the GC?
FDCs
CD4 helper T cells
What conditions can cause a lymphadenopathy?
Reactive (inflammatory and infective): localised infection in the area of drainage, systemic infection (usually viral), non-infective systemic disease (e.g. RA, SLE), drugs
Neoplastic: lymphomas, leukaemic infiltration, metastases
When is a lymphadenopathy considered significant?
Dependent on age of patient and size of lymph nodes (generally cause for concern when <1-2cm)
What histological features are seen in an acute non-specific lymphadenitis?
Neutrophil infiltration
Oedema
Follicular hyperplasia
How does an acute non-specific lymphadenitis present and what is the most common cause?
Nodes are large and painful
Usually caused by microbial infection
What causes pain in a lymphadenitis?
Lymph node capsule contains pain fibres which are stimulated when the capsule is stretched
What are the 4 patterns of chronic non-specific lymphadenitis?
Follicular hyperplasia Paracortical Sinus histiocytosis Graulomatous inflammation Mixed pattern
What causes follicular hyperplasia in chronic non-specific lymphadenitis?
Stimuli that activate humoral immune responses (e.g. autoimmune disease, microbial infection)
What causes chronic paracortical lymphadenitis?
Stimuli that activate cellular immune responses (e.g. viral infections, certain drugs)
What causes sinus histiocytosis?
Increase in macrophages in sinuses, caused by a non-specific stimulus (e.g. draining cancers, infection)
What is a more common cause of neoplastic lymphadenopathy: primary or secondary tumours?
Secondary
What types of tumours readily metastasise to lymph nodes and which do not?
Many carcinomas, melanomas, germ cell tumours readily metastasise to lymph nodes
Sarcomas do not metastasise to nodes readily
What is classification of neoplastic proliferations of haemopoietic and lymphoid tissues based on?
Cell lineage
Morphology
Immunophenotypic profiles +/- genetic abnormalities
Clinical features (to some extent)
List 5 types of lymphoid neoplasms
Precursor B cell neoplasms
Precursor T cell neoplasms
Peripheral/mature B cell neoplasms
Peripheral/mature T cell and NK cell neoplasms
Hodgkin lymphoma (neoplasms of Reed Sternberg cells and their variants)
